ToME: the Tales of Maj'Eyal

With a mastery amulet, Wildfire is giving me 100% resistance to self-inflicted fire damage. I also have 20% fire resistance, and a total of 86% fire resistance penetration.

I'm still taking 8-10% fire damage from my own spells. Any idea why?

Wild guess: resistance cap?

Well, my resistance cap is 70 (no increases). But that shouldn't be relevant with 20% resistance and 80% resistance penetration. And if the resistance cap affects Wildfire directly, I shouldn't expect to see over 90% resistance at all.

Edit: Hm. Nothing in particular changed that I can think of, but after changing levels (in both senses) a couple of times, I am now taking 0 damage and all is as it should be.